--cache-from issue with config.Cmd

test.sh

#!/bin/bash
set -eux

docker rmi cache test || true

docker build -t cache --label "ref=12345" - <<EOF
FROM alpine
ENV VAR value
EOF

# Should be /bin/sh
docker inspect cache -f '{{ .Config.Cmd }}'

# save/rmi/load the image. The bug also exists with push/rmi/pull
docker save cache -o image.tar
docker rmi cache
docker load -i image.tar

# Should still be /bin/sh
docker inspect cache -f '{{ .Config.Cmd }}'

# Same than above, but without the --label and with --cache-from
docker build --cache-from=cache -t test - <<EOF
FROM alpine
ENV VAR value
EOF

# *NOT* /bin/sh
docker inspect test -f '{{ .Config.Cmd }}'